November 13th, 2019

лошадь, диаграмма, Фейнман

Ульрик Уггерхёй снова проявился

Напоминает об идее использования кристалла как источника интенсивного поля.

Testing strong-field QED close to the fully non-perturbative regime using aligned crystals: https://arxiv.org/abs/1911.04749

Processes occurring in the strong-field regime of QED are characterized by background electromagnetic fields of the order of the critical field F_{cr} = m^2 c^3 / ℏ|e| in the rest frame of participating charges. It has been conjectured that if in their rest frame electrons/positrons experience field strengths of the order of F_{cr} / α^{3/2} ≈ 1600 F_{cr}, with α ≈ 1/137 being the fine-structure constant, their effective coupling with radiation becomes of the order of unity. Here we show that channeling radiation by ultrarelativistic electrons with energies of the order of a few TeV on thin tungsten crystals allows to test the predictions of QED close to the fully non-perturbative regime by measuring the angularly resolved single photon intensity spectrum. The proposed setup features the unique characteristics that essentially all electrons 1) undergo at most a single photon emission and 2) experience at the moment of emission and in the angular region of interest the maximum allowed value of the field strength, which at 2TeV exceeds Fcr by more than two orders of magnitudes in the rest frame of the electron.
Comments: 5 pages, 3 figures
лошадь, диаграмма, Фейнман

Как Максвелл выводил силу Лоренца :)

Maxwell's derivation of the Lorentz force from Faraday's law: https://arxiv.org/abs/1911.04605

In a brief but brilliant derivation that can be found in Maxwell's 1861 and 1865 papers as well as in his Treatise, he derives the force on a moving electric charge subject to electric and magnetic fields from his mathematical expression of Faraday's law for a moving circuit. Maxwell's derivation of this force, which is usually referred to today as the Lorentz force, is given in detail in the present paper using modern notation.
Comments: 4 pages, EuCAP 2020
лошадь, диаграмма, Фейнман

Увлекательная история формул на плитках пола в Вюрцбургском университете

Mathematics underfoot: The formulas that came to Wuerzburg from New Haven: https://arxiv.org/abs/1911.02226

Two formulas are set in floor-tiles in the foyer of the Wuerzburg building that houses the laboratory in which Wilhelm Roentgen discovered X-rays in 1895. But what do they mean, and what have they got to do with Roentgen or his work? The answers involve two distinguished professors and their PhD students, working on opposite sides of the Atlantic in the 19th Century.